With the rapid development of display industry and lighting industry, the brightness demands in the display industry and lighting industry have significantly raised. When the brightness of one single light emitting element is not enough, another light emitting element can be connected in series for increasing the brightness. Connecting another light emitting element in series can increase the light emitting area, however, the areal resistance of the light emitting elements is increased, accordingly. Because the areal resistance of the light emitting elements is increased, the lost voltage on the light emitting area is increased and thus, the power consumption is increased. Meanwhile, the increase of the light emitting area can cause heating phenomenon which is more serious. The usage reliability of the light emitting elements will be severely influenced.